The present invention relates to a new and improved apparatus and method for use in casting a plurality of articles in a mold structure.
A mold structure having a plurality of article molds disposed in an array with an open central portion and a gating system extending across an upper end of the open central portion of the array of article molds is disclosed in U.S. Pat. No. 3,690,368 issued Sept. 12, 1972 and entitled Casting Single Crystal Articles. This patent teaches that thermal gradients within a mold structure and the rate of solidification of molten metal can be controlled by surrounding the article molds with metal which is being cast. The forming of the cavities which surround the article molds complicates the making of the mold structure. In addition, the filling of the cavities surrounding the article molds with molten metal increases the quantity of molten metal required to cast articles.
The use of a baffle plate to retard the transfer of heat from article molds is disclosed in U.S. Pat. No. 3,714,977 issued Feb. 6, 1973 and entitled Method and Apparatus for the Production of Directionally Solidified Castings. The baffle plate is in the form of an annular disk which has an inner edge which surrounds and closely fits the mold structure at a location adjacent to a chill plate upon which the mold structure is supported. When the chill plate and mold structure are lowered from a furnace, the baffle plate is supported by flanges connected with the furnace and remains stationary during continued lowering of the chill plate and mold structure. The baffle plate is not disposed between article molds and is ineffective to retard heat transfer on paths which are disposed between the article molds.
A method and apparatus for use in casting a plurality of articles in a mold structure having a plurality of article molds disposed in an array with an open central portion is disclosed in U.S. Pat. No. 3,810,504 issued May 14, 1974 and entitled Method for Directional Solidification. The apparatus disclosed in this patent includes an annular chill plate upon which the mold structure is supported. A baffle plate is disposed in a central portion of the array of article molds and is supported by an inner heat sink or chill. During withdrawal of the mold from the furnace, the mold moves downwardly between inner and outer heat sinks. The combination of the annular chill plate and inner and outer heat sinks results in a relatively complicated apparatus which is difficult to operate and maintain.
A mold structure having a plurality of article molds disposed in an array with an open central portion is disclosed in Patent Cooperation Treaty International Application No. PCT/US/8600166 filed Jan. 28, 1986 and entitled Method and Apparatus for Casting Articles and in corresponding U.S. Pat. No. 4,673,021. This application and corresponding U.S. Patent disclose the concept of obtaining a large temperature gradient with a baffle which blocks the radiation of heat from the open central portion of the array of article molds as they are withdrawn from a furnace.
The mold structure disclosed in the aforementioned Patent Cooperation Treaty Application and U.S. Patent includes a gating or molten metal distribution system which is separate from the article molds. The baffle is supported by a downwardly extending support post which is connected with the gating system. The gating system is connected with the furnace. The construction of the gating system is complicated by the necessity of forming the baffle with its support post extending from the gating system. In addition, when the mold structure is used, the gating system must be connected with the furnace.